1. Field of the Invention
The present invention relates to an image pickup apparatus, and particularly to an image pickup apparatus having an AF (auto-focusing) function.
2. Description of the Related Art
In image pickup apparatuses such as digital cameras, a technique for performing focus detection according to a pixel signal outputted from an image pickup device has been proposed. Here, focus detection refers to detecting a focus position (focusing condition) of an optical imaging system with respect to an object in an image pickup apparatus. To be specific, there is proposed a focus detection method called a phase-difference detection scheme, in which a pixel group for photographing that receives a light flux that has passed through an optical imaging system and outputs pixel signals and a plurality of pixel groups for focus detection that receive only a light flux that has passed through a different pupil region of the optical imaging system and output pixel signals are respectively provided in an image pickup device, and focus detection is performed according to a phase difference of pixel signals outputted from the plurality of pixel groups for focus detection. Moreover, a focus detection method called a contrast detection scheme has been brought into use in recent years, which performs focus detection according to the magnitude of a high-frequency component quantity contained in the signal component outputted from the above described pixel group for photographing.
For example, Japanese Patent Application Laid-Open Publication No. 2009-244429 discloses a technology of an image pickup apparatus for performing an AF operation for an image pickup region of an image pickup device during live view, in which a contrast AF is performed in accordance with an in-focus position obtained by a contrast detection scheme on the image within an AF frame set in the image pickup region, by utilizing the result of performing a phase difference AF according to the in-focus position obtained by a phase-difference detection scheme and position information of a focus lens provided in the image pickup apparatus.